JP2015114338A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which includes a corona charger for charging a photoreceptor and is capable of outputting a such toner image for tilt adjustment of the corona charger that a slight change in charge potential of a photoreceptor surface can be visually recognized as a change in density of the toner image even when a charge amount of toner is varied.SOLUTION: The image forming apparatus can be operated in an analog image output mode of outputting a plurality of adjustment toner images for adjusting a gap between a corona charger and a surface of a photoreceptor in a lengthwise direction of the corona charger without substantially forming an electrostatic latent image by exposure means on the surface of the photoreceptor charged with the corona charger. In the analog image output mode, a toner image formed so as to have an average density within a range of 0.4 to 0.8 in the case of a charge amount per unit mass of toner being 30μ C/g and a toner image formed so as to have an average density within a range of 0.4 to 0.8 in the case of a charge amount per unit mass of toner being 45μ C/g are outputted.

Description

  The present invention relates to an image forming apparatus using an electrophotographic process such as a copying machine, a printer, a facsimile machine, and a multifunction machine having a plurality of these functions.

  In an image forming apparatus such as a copying machine that forms a toner image by developing an electrostatic latent image formed on a photoreceptor with toner and transfers the toner image to a transfer sheet as a recording material to form an image. The surface potential in the main scanning direction of the photoconductor may become non-uniform due to variations in the distance between the corona charger and the photoconductor in the main scanning direction of the photoconductor (inclination of the corona charger). Therefore, for example, toner fog may occur in a part of the photoconductor in the main scanning direction.

  Conventionally, in order to solve the above problem, for example, according to Patent Document 1, in an analog image forming apparatus, a white reference original is copied and recorded based on an electrostatic latent image formed by irradiation of the original image at that time. An adjustment toner image is formed on the material. Then, it is disclosed to adjust the inclination of the corona charger with respect to the photoreceptor based on the density of the toner image for adjustment.

  However, since Patent Document 1 uses an analog development (regular development) system, an adjustment toner image is formed in a region corresponding to an exposure portion that is a bright portion exposed from the exposure means.

  Accordingly, the density of the toner image on the recording material fluctuates due to the influence of variations in the exposure amount of the exposure means. Therefore, if the exposure amount of the exposure means is non-uniform, the density fluctuation due to the inclination of the corona charger will be reduced. It is difficult to measure accurately and tilt adjustment with high accuracy cannot be performed.

  Therefore, according to Patent Document 2, in the image forming apparatus that adjusts the inclination of the corona charger with the toner image output on the recording material, the accuracy of the adjustment of the inclination of the corona charger is increased by the variation in the exposure amount of the exposure unit. In order to suppress the decrease, there has been proposed a technique for forming a toner image for adjusting the inclination of the corona charger by causing the toner to adhere to the dark portion potential on the surface of the photoreceptor without exposure by the exposure means.

Japanese Patent Laid-Open No. 06-102740 JP 2009-31768 A

  In Patent Document 2, a toner image for adjusting the inclination of one corona charger in a state where the development contrast, which is the potential difference between the DC voltage value of the developing bias and the potential of the surface of the photoreceptor on which the toner image is formed, is fixed to one. Was forming.

  However, in the configuration in which an adjustment toner image having a single development contrast is formed as in Patent Document 2, the toner charge amount decreases as the toner deteriorates due to endurance use, whereby the density of the adjustment toner image is reduced. In some cases, it becomes difficult to visually recognize minute changes in the density of the toner image for adjustment in response to minute changes in the surface potential of the photoreceptor due to the tilt of the corona charger. It was. Therefore, there is a problem that the inclination of the corona charger cannot be recognized and the inclination adjustment of the corona charger cannot be performed with high accuracy.

  Therefore, the present invention is for adjusting the inclination of a corona charger that can visually recognize a minute change in the charging potential on the surface of the photoreceptor as a change in toner image density even when the charge amount of the toner fluctuates. An object of the present invention is to provide an image forming apparatus capable of outputting a toner image.

Therefore, an image forming apparatus according to the present invention includes a photoconductor, a corona charger that is provided to face the surface of the photoconductor, and charges the surface of the photoconductor, and the corona charger that is charged by the corona charger. An exposure unit that exposes the surface of the photoconductor to form an electrostatic latent image on the surface of the photoconductor, and the electrostatic latent image formed by the exposure unit is developed with toner, and a toner image is formed on the surface of the photoconductor An electrostatic latent image is formed on the surface of the photosensitive member charged by the corona charger by the exposing unit. The developing unit forms a toner image formed on the photosensitive member. A first mode in which a toner image formed on the surface of the photoconductor by the developing unit is transferred to a recording material and output; and the surface of the photoconductor charged by the corona charger is exposed by the exposure unit. Electrostatic latent image A plurality of toner images formed on the surface of the photoconductor by the developing means are transferred to a recording material without substantially performing the composition, and the distance from the surface of the photoconductor in the longitudinal direction of the corona charger is adjusted. Execution means for executing a second mode for outputting as a plurality of adjustment toner images for
The execution means is in the second mode,
A toner image formed so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g, and the charge amount per unit mass of the toner is 45 μC / g In this case, a toner image formed so that an average density is within a range of 0.4 to 0.8 is output as the plurality of adjustment toner images.

  According to the present invention, even when the charge amount of the toner fluctuates, a minute change in the charged potential on the surface of the photoreceptor can be visually recognized as a change in the density of the toner image.

1 is a cross-sectional view schematically illustrating an example of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating an example of an image forming unit according to an embodiment of the present invention. It is a principal part block diagram of the grid electrode 22a in the Example of this invention. It is a figure showing the operation panel and execution button for instruct | indicating execution of the analog image output mode based on the Example of this invention. It is a flowchart figure of the analog image output mode which concerns on the Example of this invention. It is a figure which shows an example of the several toner image for adjustment output at the time of analog image output mode implementation based on a present Example. It is a flowchart at the time of the density | concentration measurement which concerns on the Example of this invention. It is the figure which showed the high voltage | pressure application condition which concerns on the Example of this invention. It is the figure which showed an example of the charger inclination adjustment means which concerns on the Example of this invention. It is the figure which showed an example of the charger inclination adjustment means which concerns on the Example of this invention. It is a figure which shows an example of the several toner image for adjustment output at the time of analog image output mode implementation based on the Example of this invention. It is the figure which showed the high voltage | pressure application condition which concerns on the Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these is abbreviate | omitted suitably. Note that the dimensions, materials, shapes, relative positions, and the like of the component parts are not intended to limit the scope of application of this technical idea only to those unless otherwise specified.

  The image forming apparatus of this embodiment will be described with reference to the drawings. First, a schematic configuration of the image forming apparatus will be described with reference to FIG. Thereafter, the charger inclination adjustment control will be described.

(1) Overall configuration of image forming apparatus A schematic configuration of the image forming apparatus will be described below. FIG. 1 is a diagram showing a configuration of a tandem type image forming apparatus including an image forming unit (image forming unit) for forming an image of each color of YMCK and an intermediate transfer member. The image forming apparatus includes photoreceptors 1a to 1d (image carriers) provided in the image forming units for the respective colors and corona chargers 2a to 2d (charging devices) for charging the photoreceptors.

Around the photoconductors 1a to 1d, charging devices 2a to 2d, exposure devices 3a to 3d as exposure units, and development devices 4a to 4d as development units in order along the rotation direction of the photoconductor (counterclockwise). 4d, cleaning devices 5a to 5d, primary transfer devices 6a to 6d as transfer means, intermediate transfer body 7 and secondary transfer device 8, neutralization devices 9a to 9d, transfer material storage device 10, in-machine temperature and humidity detection means 11a to 11c , An outside temperature / humidity detecting means 12 and a fixing device 13 are disposed.
Hereinafter, the image forming unit mentioned above will be described in detail. In the description of this embodiment, only the image forming unit corresponding to the most upstream Y color in FIG. 1 will be described as a representative, but the same function is assumed for the groups b to d. deal with.

(2) Photoreceptor In this embodiment, as the photoconductors 1a to 1d, rotary drum type electrophotographic photoconductors are provided. Each of the photoreceptors 1a to 1d has a photosensitive layer formed of OPC (organic optical semiconductor) having a negative charging characteristic. The photoreceptors 1a to 1d have a diameter of 84 mm and a length in the longitudinal direction of 370 mm. The photosensitive member 1 is rotationally driven in the direction of the arrow in FIG. 1 at a process speed (circumferential speed) of about 350 mm / sec with the center of the drum as an axis.

  In addition, the photoconductor of this embodiment has a general organic photoconductor layer structure. Specifically, the photoreceptors 1a to 1d have an aluminum cylinder that is a conductive base on the radially inner side.

  And on this cylinder, suppression of light interference due to cylinder defects and suppression of the passage of holes generated in the charge generation layer, the undercoat layer in order not to disturb the transport of charges generated in the upper layer, only electrons An injection blocking layer for passing light, a charge generation layer for generating charges by light irradiation, a charge transport layer for transporting charges, and a surface protective layer for improving cleaning properties.

■ Charging device (non-contact charging member)
A corona charger (scorotron) as a charging device in this embodiment will be described below. FIG. 2 is a cross-sectional view illustrating an example of an image forming unit according to the present embodiment. As shown in FIG. 2, the corona charger 2a of this embodiment includes a discharge wire 21a as a discharge electrode, a U-shaped conductive shield 23a provided so as to surround the discharge wire 21a, and an opening of the shield. It has the grid electrode 22a installed. As shown in FIG. 2, the corona charger 2a is provided to face the surface of the photoreceptor 1a, and charges the surface of the photoreceptor 1a by discharging from the discharge wire 21a.

  Stainless steel, nickel, or tungsten is preferably used for the discharge wire 21a. In this embodiment, tungsten, which is very stable among metals, was used for the discharge wire.

  By using tungsten for the discharge wire, stable corona discharge can be performed under severe conditions such as heating and ozone environment, and stable use over a long period of time can be achieved.

As shown in FIG. 9, the discharge wire 21a is held at a constant tension by an adjusting screw 24a integrated with a conductive shield 23a made of stainless steel (hereinafter referred to as SUS) that performs an electrical shield action, and is an insulating material. The discharge wire 21a and the shield 23a are electrically insulated from each other by the holding member.
The discharge wire 2a preferably has a diameter of 40 μm to 100 μm. If the diameter of the discharge wire 21a is too small, it will be cut by collision of ions due to discharge. On the contrary, if the diameter of the discharge wire 21a is too large, the voltage applied to the discharge wire 21a becomes high in order to obtain a stable corona discharge.

  When the applied voltage is high, ozone is likely to be generated, and the probability of image flow is increased, and further, the power supply cost is increased.

  In this embodiment, a tungsten wire having a diameter of 60 μm was used as the discharge wire 21a. A rectification effect is generated by bias control of the grid electrode 22a connected to a constant voltage power source (not shown) with respect to the charge generated by the discharge wire 21a, thereby adjusting the amount of charge applied to the photoreceptor 1a. Control the charging potential.

  FIG. 3 shows a configuration diagram of a main part of the grid electrode 22a according to the present embodiment. In this embodiment, a grid electrode 22a having a plurality of openings (through holes) formed in a mesh shape is applied.

  The base material of the grid electrode 22a used in this example is a sheet metal made of austenitic stainless steel (SUS304) with a thickness of 0.03 mm, and a plurality of holes (through holes) are formed by etching. It is.

  The grid electrode 22a subjected to the etching process has a mesh shape inside. As shown in FIG. 3, the apertures are 45 ± 1 ° oblique to the base line, 0.071 ± 0.03 mm wide, and are formed at intervals of an opening width of 0.312 ± 0.03 mm.

  The grid electrode 12 is provided with a beam having a width of 0.1 ± 0.03 mm in the longitudinal direction every 6.9 ± 0.1 mm in order to prevent bending. The width of the outer frame is 1.5 ± 0.1 mm.

  The grid electrode 22a has a surface layer formed of tetrahedral amorphous carbon (hereinafter referred to as “ta-C”) on a base material formed of SUS.

  ta-C is a material that is chemically inert to discharge products generated by corona discharge and is applied in the present system as a material having excellent corrosion resistance. Hereinafter, the base material formed of SUS is referred to as “SUS base material”, and the surface layer formed of ta-C is referred to as “ta-C layer”.

  The grid electrode 22a using the ta-C layer can suppress the occurrence of oxidation and electrolytic corrosion of the SUS base material, and can maintain stable charging with little charging unevenness over a long period of time.

  The material of the base material is not limited to the austenitic stainless steel (SUS304), and other austenitic stainless steel may be used. Further, other stainless steels such as martensitic stainless steel and ferritic stainless steel may be used.

The corona charger 2a is connected to a high voltage power supply 14a as a charging bias applying means for applying a charging bias, and applies a charging bias to the discharge wire 21a and the grid electrode 22a.
The charging bias applied from the high voltage power supply 14a has a function of uniformly charging the surface of the photoreceptor 1a to a negative potential.

Specifically, a constant current control of -1 mA is applied to the discharge wire 21a, and a constant voltage of about -900v is applied to the grid electrode 22a during normal image formation in this embodiment (hereinafter referred to as the first mode in this embodiment). It is controlled to become control.
Note that the high voltage condition at the time of adjusting the inclination of the charger, which is a feature of the present invention, will be described later.

(2) Other Image Forming Unit In this embodiment, the exposure device 3a as an exposure means is a laser beam scanning exposure device using a semiconductor laser light source and a polygon mirror optical system. For example, when −1 mA is applied to the discharge wire 21a of the corona charger 2a by constant current control and −900v is applied to the grid electrode 22a, the charged potential on the photoreceptor 1a is charged to about −800v ( Dark potential). The charged surface of the photoreceptor 1a changes to about −300 V (bright portion potential) by exposure of the exposure device 3. In this way, the surface of the photoreceptor is exposed by the exposure device 3a, and an electrostatic latent image is formed on the surface of the photoreceptor.

  The developing device 4a as the developing means supplies the developer (toner) to the electrostatic latent image formed on the surface of the photoreceptor 1a by the exposure device 3a and develops it, thereby developing the electrostatic latent image as a toner image. To form a toner image on the surface of the photoreceptor 1a. The developing device 4a is a two-component magnetic brush developing type reversal developing device.

  The developing device 4a has a developing container and a developing sleeve. A two-component developer is accommodated in the developing container. The two-component developer is a mixture of toner and magnetic carrier. A two-component developer having a toner concentration (TD ratio) of 8% in which toner and carrier are mixed at a weight ratio of about 8:92 is used. The toner is a toner having an average particle diameter of about 6 μm obtained by pulverizing and classifying a pigment obtained by kneading a resin binder mainly composed of polyester. As the carrier, for example, the surface oxidation region can be suitably used metal such as unoxidized iron, nickel, cobalt, manganese, chromium, rare earth and their alloys, or oxide ferrite. The method is not particularly limited. The carrier has a volume average particle size of 20 to 50 μm, preferably 30 to 40 μm, and a resistivity of 107 Ωcm or more, preferably 108 Ωcm or more.

  Here, a carrier in which a core mainly made of ferrite is coated with a silicon resin is used, the volume average particle size is 35 μm, the resistivity is 5 × 10 8 Ωcm, and the magnetization is 200 emu / cc.

  The developing sleeve is disposed to face the photosensitive member 1a in a state where the closest distance to the photosensitive member 1a is maintained at 250 μm. A facing portion between the photoconductor 1a and the developing sleeve becomes a developing portion.

  The surface of the developing sleeve is driven to rotate in the forward direction and the moving direction of the surface of the photoreceptor 1a at the developing portion. The developing sleeve includes a magnet roller on the inner side, and the two-component developer is rotated and conveyed to the developing unit by the rotation of the developing sleeve by the magnetic force.

  The magnetic brush layer formed on the surface of the developing sleeve is layered into a predetermined thin layer by a developer coating blade, and a predetermined developing bias is applied to the developing sleeve from a developing bias applying power source as a developing bias applying means. .

  During normal image formation as the first mode, the developing bias applied to the developing sleeve is an oscillating voltage in which a DC voltage and an AC voltage are superimposed. Specifically, when the charged potential on the surface of the photoreceptor 1a is −800v, a DC voltage of −620v, an AC voltage of 1300Vpp, and a frequency of 10 kHz are applied. The toner in the two-component developer is selectively attached to the electrostatic latent image on the photoreceptor 1a by the electric field due to the developing bias. As a result, the electrostatic latent image is developed as a toner image.

  At this time, the charge amount of the toner developed on the photoreceptor 1a is about 40 μC / g. The developer on the developing sleeve that has passed through the developing portion is continuously returned to the developer reservoir in the developing container as the developing sleeve rotates.

  The charge amount of the toner to be developed varies depending on durability and environment. When the toner is new, the charge amount of the toner is relatively high, but the toner and carrier due to use deteriorate and the charge amount of the toner decreases. Also, the toner charge amount varies depending on the environment. Therefore, for example, by controlling the discharge of deteriorated toner out of the developing device and replenishing new toner from the toner bottle or agitating the toner and the carrier, the charge amount of the toner is hindered in normal image formation. The control is adjusted so that it does not come out. In this embodiment, the above-described control is performed so that the charge amount per unit mass of the toner is within the range of 10 μC / g to 45 μC / g. However, the charge amount of the toner varies within the above range. For example, the charge amount of a new toner is relatively high and is 40 μC / g or more. However, the charge amount of the toner decreases to, for example, about 30 μC / g due to deterioration with use.

  In this embodiment, the intermediate transfer belt 7 (intermediate transfer member) and the transfer roller 6a are applied as means for transferring the toner image on the photosensitive member 1a. The transfer roller 6a is pressed against the surface of the photoconductor 1a via the intermediate transfer belt 7 with a predetermined pressing force, and the pressure nip portion between the two is a transfer portion. The transfer roller 6a preferably has a resistance value of 1 × 10 2 to 1 × 10 8 Ω / □ when +2 kv is applied in a measurement environment at a temperature of 23 ° C. and a humidity of 50%.

  In this example, an ion conductive sponge roller formed by mixing nitrile rubber and ethylene-epichlorohydrin copolymer and having an outer diameter of 16 mm and a core metal diameter of 8 mm was used.

  The intermediate transfer belt 7 is conveyed while being sandwiched between the photoreceptor 1a and the transfer roller 6a. The intermediate transfer member used in the present embodiment employs a belt having an elastic layer with a soft surface in order to cope with diversified recording materials. The intermediate transfer belt prevents a recording material with uneven surface from being transferred and prevents a transfer defect called “slow-out” which is likely to occur on coated paper or OHP paper. The intermediate transfer belt 7 has a three-layer structure of a base material, an elastic layer, and a coat layer, and has a total thickness of about 360 μm. The substrate is made of a conductive polyimide resin material having a thickness of 80 to 90 μm. The elastic layer is formed by laminating 200 to 300 μm of chloroprene rubber on a substrate, and has a JIS-A hardness of 60 degrees. The coat layer is for securing the releasability of the supported toner particles and recording material, and is the outermost layer having a thickness of about 5 to 15 μm in which a fluororesin is dispersed in a polyurethane resin binder.

  The resistance of the intermediate transfer belt 7 is adjusted such that the volume resistivity is 1 × 10 9 to 1 × 10 11 Ω · cm, and the surface resistivity is adjusted to 1 × 10 11 to 1 × 10 13 Ω / □. At the time of image formation, a positive transfer bias voltage (for example, +1500 v) having a polarity opposite to the negative polarity that is the normal charging polarity of the toner is applied to the transfer roller 6a. As a result, the toner images on the photoreceptor 1a are sequentially electrostatically transferred onto the surface of the intermediate transfer member.

  The toner image transferred onto the intermediate transfer member 7 is transferred to the recording material by the recording material conveyed from the recording material storage device 10 and the secondary transfer device 8 as a transfer means. The recording material onto which the toner image has been transferred is heated and pressurized by the fixing device 13, and the toner image is melted and fixed, and is output to the outside of the image forming apparatus.

  The cleaning device 5a is a device for cleaning the transfer residual toner that is not transferred to the intermediate transfer member 7 and remains on the photosensitive member. Although blade cleaning is applied in this embodiment, the present invention is not limited to this, and a fur brush or the like may be added.

  The control unit (not shown) is a normal computer control device programmed with a calculation function such as a CPU, for example, and comprehensively controls each unit of the image forming apparatus to execute image formation.

■ Analog image output mode (second mode)
As will be described later, the image forming apparatus according to the present exemplary embodiment does not substantially form an electrostatic latent image by the exposure unit, and charges the corona charger within at least one output image range. This is a potential difference between the DC voltage value of the developing bias and the potential of the area where the toner image is formed on the surface of the photosensitive member by changing at least one of the high-voltage charging bias and the developing bias applied to the developing device by two or more levels. There is an analog image output mode as a second mode in which a plurality of toner images for adjusting the inclination of corona chargers having different development contrasts are developed (analog development), transferred to a recording material and automatically output. An operator or a serviceman visually confirms density unevenness (change in density in the main scanning direction) of the toner image for adjustment on the recording material output in this mode in the main scanning direction (rotation axis direction of the photoreceptor 1a). To do. If it is determined that the corona charger is tilted with respect to the surface of the photoconductor, the tilt of the corona charger with respect to the rotation axis direction of the photoconductor 1a based on the confirmation result of the output adjustment toner image ( The distance between the corona charger and the surface of the photosensitive member in the longitudinal direction) can be adjusted. In this embodiment, the inclination angle of the discharge wire 21a and the grid electrode 22a of the charging device 2a shown in FIG. 2 can be changed in the plane perpendicular to the main scanning direction on the surface of the photoreceptor 1a. The tilt adjustment mechanism will be described later in another item.

  In this embodiment, as an input means (instruction means) for executing the analog image output mode, as shown in FIG. 4, an execution button 16 on the operation panel 15 as an operation unit provided in the main body is provided. Yes. By pressing the execution button 16, image forming conditions for outputting an analog image are set, and an adjustment toner image is automatically output.

  The control flow when executing the analog image output mode will be described below.

FIG. 5 shows a flowchart when the analog image output mode of this embodiment is executed.
S100: Control of the analog image output mode is started by pressing the execution button 16 as an input means for executing the analog image output mode by an operator or a service person.
S101: The control unit as an execution unit performs control for determining each high-voltage image output condition such as a developing bias and a charging bias during normal image formation (hereinafter referred to as a first mode).
S102: The control unit determines whether or not the control in S101 has ended normally. If the control in S101 does not end normally (at the time of abnormality), the process proceeds to S105 and error information is displayed.
S103: The control unit determines a high-pressure condition for use in the analog image output mode based on the high-pressure condition determined by the control in S101.
S104: Since the analog image output mode is different from the first mode in the image output condition, the control unit performs control that cancels the error condition and does not perform error determination. If it is determined, an error is displayed and the operation of the image forming apparatus is stopped.
S106: The control unit instructs the image forming apparatus to start analog image output.

  Next, the adjustment toner image output by executing the analog image output mode will be described with reference to FIG.

  FIG. 6 is a diagram illustrating an example of a plurality of adjustment toner images output when the analog image output mode according to the present embodiment is performed.

  In the analog image output mode in this embodiment, a plurality of adjustment toner images in the analog image output mode are formed on a single recording material having a size of 19 inches in the sub-scanning direction and 13 inches in the main scanning direction. Reference numeral 100 denotes a solid white image as a blank portion where no toner image is formed. Reference numerals 101 and 102 denote adjustment toner images formed in the analog image output mode. The two adjustment toner images have different high-pressure conditions. By setting different development contrasts, different densities are formed. Specifically, the development contrast is set so that the average density of the first adjustment toner image 101 is within the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 45 μC / g. The second adjustment toner image 102 is adjusted by setting the development contrast so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g. A toner image is formed. As a result, two adjustment toner images of the first adjustment toner image 101 and the second adjustment toner image 102 whose average density is lower than that of the first toner image 101 are formed on one recording material. become. The average density referred to here is the average density of the entire toner image area. For example, the total density at three ends of the toner image in the main scanning direction is measured, and the average value is obtained. Also good. The density of the toner image for adjustment is preferably a halftone density range in which a minute change in density due to a minute change in the charged potential on the surface of the photoreceptor can be easily visually confirmed. It was found that the change in density is easily recognized by visual observation. Further, the density in the present embodiment is a numerical value obtained by using a reflection densitometer manufactured by X-Rite for the density of an analog image output using Canon white paper GFC081 manufactured by Canon as a recording material. What is necessary is just to adjust appropriately the absolute value of the density | concentration adjusted with the output medium and a reflection densitometer.

  In this embodiment, the recording material to be used can be saved by forming a plurality of adjustment toner images on one recording material. However, the present invention is not limited to this. One recording material is used for each recording material. An adjustment toner image may be formed.

  Here, the setting and timing of the high voltage application condition when executing the analog image output mode in the present embodiment will be described with reference to FIG.

  FIG. 8 is a diagram showing the timing of high voltage application according to the embodiment of the present invention.

  In the control in FIG. 8A, the DC voltage superimposed on the development bias as the development high voltage applied to the developing means is set to the same voltage value as the DC voltage superimposed on the development bias at the time of normal image formation which is the first mode. Then, by setting the charging bias as the charging high voltage to different values for the first adjustment toner image and the second adjustment toner image, different development contrasts are set to form analog images. . The detailed high pressure setting conditions are described below.

  In this control, the photosensitive member 1a is rotated with the exposure device 3a turned off. Next, in order to form a solid white image 100 as a blank portion where no toner image is formed, a charging high voltage is applied so that the charging potential (V [5]) on the surface of the photosensitive drum 1a is −800v.

  The charging high voltage in this embodiment was set to a constant current control of −1 mA for the discharge wire 21a and a constant voltage control of −900 V to the grid electrode 22a under the high voltage conditions during normal image formation. Here, the position where the charging potential is set to −800 V is a predetermined position in the longitudinal direction of the photosensitive member, and specifically, a potential sensor capable of detecting a part of the charging potential in the longitudinal direction of the photosensitive member is provided. If it is, it is a charging potential at a position that can be detected by the electric sensor in the longitudinal direction.

  A developing high voltage (V [1]) is applied together with the charging high voltage. In this embodiment, a developing bias in which an AC voltage having a frequency of 10 kHz and 1300 vpp is superimposed on a DC voltage of −620 v is applied as a developing high voltage.

  Next, in this embodiment, in order to form the adjustment toner images 101 and 102, two types of adjustment toner images having different development contrasts can be created by changing the DC voltage value applied to the grid electrode 22a. It becomes.

  In this embodiment, the DC voltage value applied to the grid electrode 22a is −720v, V when V [2] so that the charged potential on the surface of the photoreceptor 1a becomes V [2] = − 650v, V [3] = − 700v. [3] Occasionally set to -780V.

  When the charged potential on the surface of the photoconductor 1a changed at a predetermined timing passes through the development nip, analog development is performed, and a first adjustment toner image and a second adjustment toner image are formed. When the development of the adjustment toner image is completed, the solid white image 100 is formed by returning to the condition for forming the solid white image 100 as a blank portion where the toner image is not formed, and the control ends.

  As described above, by forming the solid white image 100 as a blank portion where no toner image is formed at both ends in the conveyance direction of the recording material, the toner image formed in the analog image output mode protrudes from the recording material region. As a result, the secondary transfer device 8 can be prevented from becoming dirty.

  In this embodiment, the control example of the analog image output mode for Y color has been described as a representative. However, an adjustment toner image for Y to K colors may be formed on one recording material and output. In this case, it is preferable to form the adjustment toner image groups of the respective colors so as not to overlap each other. Similarly, when outputting separately to a plurality of recording materials, it is preferable to form the toner image groups for adjustment of each color so as not to overlap each other.

  In this embodiment, the voltage applied to the grid electrode is set so that the charged potential on the surface of the photoreceptor in the region detectable by the potential sensor in an environment of temperature 23 ° C. and humidity 50% becomes a predetermined potential. The setting method is not particularly limited.

  For example, the high-pressure conditions may be changed by using the temperature / humidity detection means 11a to 11c and 12 shown in FIG.

  Further, the present invention is not limited to the configuration including the potential sensor, and the relationship between the potential of the photoconductor and the charging bias is stored in advance without the potential sensor, and the charging bias is set based on the relationship. May be.

  After executing the analog image output mode, the operator or service person visually confirms the output adjustment toner image. Of the plurality of toner images for adjustment, when a difference in density is detected between both ends in the main scanning direction, it is determined that the corona charger is tilted, and the corona charger 2a, which will be described later, is used to adjust the corona. The distance between the surface of the photoreceptor and the corona charger in the longitudinal direction of the charger is adjusted.

  If there is a densitometer that can measure the density of the toner image for adjustment, a densitometer can also be used. In this case, the image density at the center position in the main scanning direction of each adjustment toner image is measured using a reflection densitometer manufactured by X-Rite, and the adjustment toner image having a density of 0.6 ± 0.2 is selected. To do.

  Then, the density of both ends of the selected adjustment toner image in the main scanning direction is measured, and when there is a density difference larger than 0.02 between the both ends, a corona described later so that the density difference becomes 0.02 or less. Adjustment is performed using the inclination adjusting means of the charger 2a.

FIG. 7 shows an execution flow by a service person or an operator at the time of concentration measurement using a densitometer.
S200: The adjustment toner image is output from the image forming apparatus by executing the analog image forming mode.
S201: The density of the central position in the main scanning direction of the toner image for adjustment output by the service person or the operator, and the density of the black-filled portion 104 shown in FIG. 6 are measured.
S202: The service person or operator selects an adjustment toner image whose measured density is in the range of density 0.6 ± 0.2.
S203: The service person or the operator measures the density of both ends of the selected adjustment toner image in the main scanning direction, and the density of the black and black areas 105 and 106 shown in FIG.
S204: The service person or the operator determines whether the density difference between both ends is greater than 0.02.
S205: If the serviceman or the operator determines that the density difference between both ends is greater than 0.02, the process proceeds to the corona charger inclination adjustment flow.
S206: If the serviceman or the operator determines that the value is 0.02 or less, the serviceman or the operator determines that the corona charger inclination adjustment is unnecessary.

■ Charger tilt adjustment means (tilt adjustment by grid electrode 22a)
The charger inclination adjusting means for adjusting the inclination of the corona charger in this embodiment will be described in detail.

  In this embodiment, the inclination of the corona charger with respect to the surface of the photoreceptor is adjusted by adjusting the inclination by the grid electrode 22a.

  As shown in FIG. 9, the grid inclination adjusting means 26 a includes a support piece 27 as a support portion, fixing screws 27 a and 27 b as fixing means, a position adjusting member 29, and a screw member 28.

FIG. 9A is a view of the adjustment mechanism as viewed from the front, and FIG. 9B is a cross-sectional view thereof.
The support piece 27 provided on one end side of the corona charger 2a has a first inclined surface 29a attached to the block 30 via fixing screws 27a and 27b. The support piece 27 is fixed to the block 30 by fastening the fixing screws 27a and 27b screwed from the front cover 31 with a tool such as a screwdriver. Further, the support piece 27 is configured to be slidable in the vertical direction (direction approaching and separating from the photoreceptor 1a) with respect to the block 30 by loosening the fixing screws 27a and 27b.

  Here, the support piece 27 is provided with charger positioning holes 27d and 27e that engage with a corona charger positioning member (not shown) of the image forming apparatus. On the other hand, a positioning member (not shown) for determining the position with respect to the image forming apparatus is also provided on the other end side, and since this side is uniquely determined, no adjustment mechanism is provided.

  Accordingly, in a state where the charger positioning holes 27d and 27e of the support piece 27 are engaged with the image forming apparatus, the block 30 can be moved toward and away from the photoreceptor 1a by loosening the fixing screws 27a and 27b. Supported by the support piece 27.

  As shown in FIG. 9, the position adjusting member 29 faces the support piece 27 in the block 30 and is arranged to be movable in the front-rear direction. Further, the position adjusting member 29 is formed with a second inclined surface 29 b that engages with the first inclined surface 29 a of the support piece 27.

  The screw member 28 is screwed to the position adjusting member 29 via the front cover 31 of the block 30. The screw member 28 is restricted from moving in the axial direction, and a screw head as an adjustment operation portion is exposed from the front cover 31.

  By rotating the head of the screw member with a tool such as a screwdriver, the screw member 28 is rotated and the position adjusting member 29 is moved in the front-rear direction. At this time, since the second inclined surface 29b of the position adjusting member 29 is engaged with the first inclined surface 29a of the support piece 27, the support piece 27 moves relative to the block 30 in the vertical direction by a cam action. Accordingly, the amount of rotation of the charger main body with respect to the photoreceptor 1a, that is, the distance between the grid electrodes with respect to the surface of the photoreceptor 1a can be adjusted by the amount of rotation.

  The grid inclination adjusting means 26a is provided at one end in the longitudinal direction of the corona charger.

  Based on the present embodiment, assuming the following two conditions when it is determined that there is a density difference at both ends and the inclination of the corona charger needs to be adjusted, the adjustment of the corona charger inclination at that time will be described.

[1] When the density of the end corresponding to the end of the corona charger on the side where the grid inclination adjusting means 26a is provided in the toner image for adjustment is thinner than the density of the other end The grid electrodes are brought closer to the photoreceptor 1a by loosening the screws 27a and 27b and rotating the screw member 28 counterclockwise.

[2] When the density of the end corresponding to the end of the corona charger on the side where the grid inclination adjusting means 26a is provided in the adjustment toner image is higher than the density of the other end. The grid electrodes are separated from the photoreceptor 1a by loosening the screws 27a and 27b and rotating the screw member 28 clockwise.

  According to this embodiment, in the analog image output mode, the first density formed so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 45 μC / g. An adjustment toner image and a second adjustment toner image formed so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g. When the toner is new and the charge amount per unit mass of the toner is relatively high and is in the vicinity of 45 μC / g, the density unevenness in the main scanning direction of the toner image is visually observed by the first adjustment toner image. Even when the charge amount per unit mass of the toner is reduced to the vicinity of 30 μC / g due to the progress of the durability of the toner, the second adjustment toner image visually confirms the main scanning method of the toner image. It is possible to confirm the non-uniformity of the concentration in. As a result, even when the charge amount of the toner changes, the distance from the surface of the photoconductor in the longitudinal direction of the corona charger can be accurately adjusted.

  In the first embodiment, in the corona charger having a grid electrode, an example in which a plurality of adjustment toner images based on a plurality of development contrasts is formed by setting a DC voltage value applied to the grid voltage as a charging high voltage is described. However, in this embodiment, a case where a plurality of toner images for adjustment are formed by controlling the DC voltage applied to the discharge wire will be described. In addition, about the structure same as Example 1, the overlapping description is abbreviate | omitted suitably by attaching | subjecting the same code | symbol.

  Under the high voltage setting condition in the analog image output mode of this embodiment, the development contrast of the plurality of adjustment toner images is set by changing the current value of the DC voltage applied to the discharge wire.

  Specifically, the current value of the DC voltage applied to the discharge wire 21a is set to V [2] so that the charging potential on the surface of the photoreceptor 1a is V [2] = − 650v and V [3] = − 700v− It was set to 0.6 μA and −0.75 μA when V [3].

  When the charged potential on the surface of the photoconductor 1a changed at a predetermined timing passes through the development nip, analog development is performed, and a first adjustment toner image and a second adjustment toner image are formed. When the development of the adjustment toner image is completed, the control is terminated after returning to the conditions for forming the solid white image 100.

■ Charger inclination adjustment means (Inclination adjustment by discharge wire 21a)
An inclination adjusting means using the discharge wire 21a in this embodiment will be described. FIG. 10 is a cross-sectional view of a main part in which only the structure of the tilt adjusting means of the corona charger 2a is extracted. 10A shows a cross section when the corona charger 2a is divided in the main scanning direction, and FIG. 10B shows an overhead view from the arrow A in the figure.

  The charger inclination adjusting means has a helical adjustment screw 24a and an adjustment piece 25a provided in contact with the conductive shield 23a, and the adjustment pieces at both ends are provided so that the discharge wire 21a is maintained at a constant tension. It has been.

  The adjusting screw 24a can be tightened or loosened with a tool such as a screwdriver. In this embodiment, the adjustment piece 25a can be raised by rotating it clockwise, and the adjustment piece 25a can be lowered by turning it counterclockwise.

  Based on this embodiment, assuming the following two conditions when it is determined that there is a difference in density between the areas of the toner image for adjustment corresponding to both ends of the corona charger and it is necessary to adjust the inclination of the corona charger, The charger inclination adjustment at that time will be described.

[1] When the density of the adjustment toner image area corresponding to F in FIG. 10 is higher than the density of the adjustment toner image area corresponding to R In FIG. 10, the adjustment screw 24a on the R side is counterclockwise. By rotating the adjustment piece 25a by rotating it, the discharge wire 21a on the R side approaches the photosensitive member side.

  As a result, the potential on the back side can be charged to the potential at the center position of the image, and the density difference at both ends can be adjusted to be within the density standard. Desirably, the adjustment piece 25a on the F side is also rotated and adjusted in the clockwise direction, so that it is possible to cope with an adjustment that exceeds the movable limit of the adjustment screw on the R side.

[2] When the density of the adjustment toner image area corresponding to F in FIG. 10 is thinner than the density of the adjustment toner image area corresponding to R In FIG. 10, the adjustment screw 24a on the F side is counterclockwise. By rotating the adjustment piece 25a by rotating it, the F-side discharge wire 21a approaches the photosensitive member side.

  As a result, the potential on the back side can be charged to the potential at the center position of the image, and adjustment within the density standard can be performed. Desirably, the adjustment piece 25a on the R side is also rotated and adjusted, so that even when an adjustment exceeding the movable limit of the adjustment screw on the F side occurs, it is possible to cope.

  According to this embodiment, even when the charge amount of the toner changes, it is possible to accurately adjust the distance from the surface of the photoreceptor in the longitudinal direction of the corona charger.

  In Example 1 and Example 2, as the plurality of toner images for adjustment in the analog image output mode, the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 45 μC / g. The first toner image for adjustment formed so as to be within, and formed so that the average density is within the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g. The example of outputting the second toner image for adjustment described above has been described.

  In this embodiment, as described in the first embodiment, control is performed to adjust the charge amount of the toner within a range that does not hinder normal image formation. For this reason, there are few cases where the charge amount per unit mass of the toner decreases to the lower limit of 10 μC / g in the above-mentioned range, but when the toner or the carrier further deteriorates, the charge amount per unit mass of the toner is increased as described above. The lower limit in the measured range may be reduced to 10 μC / g. In that case, the average density of the first and second adjustment toner images may be outside the range of 0.4 to 0.8.

  Therefore, in this embodiment, when the charge amount of the toner assumed in the second adjustment toner image is further reduced, a slight change in the charged potential on the surface of the photoreceptor is visually observed as a change in the toner image density. A third adjustment toner image that can be confirmed is further formed and output.

  Specifically, the control unit, which is an execution unit, is further formed so that the average density is within the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 10 μC / g. 3 adjustment toner images are output as one of the plurality of adjustment toner images.

  FIG. 11 is a diagram illustrating an example of a plurality of adjustment toner images output when the analog image output mode according to the present embodiment is performed.

  In the analog image output mode in this embodiment, a plurality of adjustment toner images in the analog image output mode are formed on a single recording material having a size of 19 inches in the sub-scanning direction and 13 inches in the main scanning direction. Reference numeral 100 denotes a solid white image as a blank portion where no toner image is formed, and 101, 102, and 103 denote a plurality of adjustment toner images formed in the analog image output mode. Different development contrasts are obtained by changing the high-pressure conditions to obtain different densities. Specifically, the development contrast is set so that the average density of the first adjustment toner image 101 is within the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 45 μC / g. The second adjustment toner image 102 is set with a development contrast so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g. The adjustment toner image 103 of No. 3 is adjusted with the development contrast so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 10 μC / g. Is formed. As a result, the first adjustment toner image 101, the second adjustment toner image 102 having a lower average density than the first adjustment toner image 101, and the second adjustment toner image are recorded on one recording material. Three adjustment toner images of the third adjustment toner image having an even lower average density than that are formed.

  Also in this embodiment, one adjustment toner image may be formed on each of a plurality of transfer materials.

  Here, the setting and timing of the high voltage application condition when executing the analog image output mode in the present embodiment will be described with reference to FIG.

FIG. 12 is a diagram showing a high voltage application timing according to the embodiment of the present invention.
In the control in FIG. 12A, the DC voltage of the developing bias applied as the developing high voltage applied to the developing means is set to the same voltage value as in the normal image formation which is the first mode, and the charging bias as the charging high voltage is set to the first voltage. By setting different values for the one adjustment toner image, the second adjustment toner image, and the third adjustment toner image, different development contrasts are set to form analog images. The detailed high pressure setting conditions are described below.

  Also in this control, the photosensitive member 1a is rotated with the exposure device 3a turned off. Next, in order to form the solid white image 100, a charging high voltage is applied so that the charging potential (V [5]) on the surface of the photosensitive drum 1a becomes −800v.

  Also in this embodiment, the developing high voltage (V [1]) is applied together with the charging high voltage. In this embodiment, a developing bias in which an AC voltage having a frequency of 10 kHz and 1300 vpp is superimposed on a DC voltage of −620 v is applied as a developing high voltage.

  Next, in order to form the adjustment toner images 101 to 103, in this embodiment, a plurality of adjustment toner images can be created by sequentially changing the DC voltage value applied to the grid electrode 22a.

  In this embodiment, the DC voltage value applied to the grid electrode 22a is set to V so that the charging potential on the surface of the photoreceptor 1a becomes V [2] = − 650v, V [3] = − 700v, V [4] = − 750v. It was set to -720v for [2], -780v for V [3], and -840v for V [4].

  When the charged potential on the surface of the photoconductor 1a changed at a predetermined timing passes through the development nip, the analog development is performed, and the first adjustment toner image, the second adjustment toner image, and the third adjustment toner image. Is formed. When the development of the adjustment toner image is completed, the control is terminated after returning to the conditions for forming the solid white image 100.

  In this embodiment, the first, second, and third toner images for adjustment may be formed by changing the direct current value applied to the discharge wire as in the second embodiment.

  According to this embodiment, even when the charge amount of the toner assumed in the second adjustment toner image is further reduced, a slight change in the charged potential on the surface of the photoreceptor is visually observed as a change in toner image density. Thus, it is possible to accurately adjust the distance from the surface of the photoconductor in the longitudinal direction of the corona charger.

  In the first to third embodiments, an example in which a plurality of types of adjustment toner images are formed by setting a plurality of types of charging high voltage has been described.

  However, as a high pressure setting condition for forming an adjustment toner image, a plurality of development high pressures may be set without changing the charging high pressure, and both the charging high pressure and the development high pressure may be changed. Also good.

Here, a high voltage application condition in each component in the present embodiment will be described with reference to FIG.
In the control in FIG. 12B, an adjustment toner image is formed by applying a charging high voltage at the same setting as that during normal image formation (first mode) and changing the development high voltage conditions. The detailed high pressure setting conditions are described below.

  In this control, the photosensitive member 1a is rotated with the exposure device 3a turned off. Next, in order to form the solid white image 100, a high voltage is applied so that the charging potential (V [10]) on the surface of the photoreceptor 1a is −800v) and the DC voltage value V [6] = − 620v of the developing bias. To do.

  In this embodiment, the charging bias as the charging high voltage is constant current control of -1 mA for the discharge wire 21a and -900v constant voltage control for the grid electrode 22a.

  Next, in this embodiment, in order to form the adjustment toner images 101 to 103, an adjustment toner image can be created by sequentially changing the development high-pressure conditions.

  In this embodiment, a DC voltage is applied to the developing device 4a so that V [7] = − 650v, V [8] = − 700v, and V [9] = − 750v, and the AC voltage is commonly 10 kHz. 1300 Vpp was applied.

  Analog development is performed as a toner image for adjustment when the photoreceptor 1a passes the development nip under the development high-pressure condition changed at a predetermined timing. When the development of the predetermined adjustment toner image is completed, transferred to the recording material and output to the outside of the image forming apparatus, the condition for forming the solid white image 100 is restored and the analog image output mode is ended.

  The control in FIG. 12C applies charging high voltage and developing high voltage similar to those in the first mode only when outputting the solid white image 100, and charging high voltage and developing high voltage conditions when outputting the adjustment toner images 101 to 103. By changing both, an adjustment toner image is formed. The detailed high pressure setting conditions are described below.

In this control, the photosensitive member 1a is rotated with the exposure device 3a turned off. Next, in order to form the solid white image 100, a charging high voltage is applied so that the surface potential (V [18]) on the photosensitive member 1a is -800v).
In the present embodiment, a constant current control of -1 mA was applied to the discharge wire 21a, and a constant voltage control of -900v was applied to the grid electrode 22a. At the same time, a development high voltage (V [11]) is applied. In this embodiment, -620v is applied as a DC voltage superimposed on the development bias as the development high voltage, and a frequency of 10 kHz and 1300 vpp are applied as an AC voltage.

  Next, in this embodiment, in order to form the adjustment toner images 101 to 103, the adjustment toner image is formed by sequentially changing the condition of the DC voltage applied to the grid electrode and the condition of the DC voltage superimposed on the developing bias. create.

  In this embodiment, the voltage amount applied to the grid electrode 22a is V so that the charging potential on the surface of the photoreceptor 1a is V [15] = − 735v, V [16] = − 760v, V [17] = − 785v. A constant voltage of -820v was applied at [16], -850V at V [17], and -880v at V [18]. The DC voltage superimposed on the developing bias at a predetermined timing with respect to the change timing is set to V [12] = − 605v, V [13] = − 580v, and V [14] = − 555v. A DC voltage was applied, and the AC voltage was commonly applied at a frequency of 10 kHz and 1300 Vpp.

  Analog development is performed as a toner image for adjustment when the photoreceptor 1a passes through the development nip under the charging and development high-pressure conditions changed at predetermined timing. When the development of the predetermined adjustment toner image is completed and transferred to the recording material and output to the outside of the image forming apparatus, the condition for forming the solid white image 100 is restored and the analog image output mode ends. .

  The output image confirms the density difference at both ends in the main scanning direction as in the first embodiment, and adjusts the inclination of the corona charger according to the density difference, thereby achieving the same effect as in the first embodiment. Can be played. Since the adjustment method is the same as that of the first embodiment, it is omitted.

  Further, in the present embodiment, a predetermined development high pressure value is applied in an environment of a temperature of 23 ° C. and a humidity of 50%, but is not limited to this value.

  Also according to this embodiment, the same effects as those of Embodiments 1 to 3 described above can be obtained.

  Although the embodiment of the present invention has been described above, in the formation of the adjustment toner image in the analog image output mode in the first to fourth embodiments, the exposure device 3a as the exposure unit is turned off. The latent image is not substantially formed ", and the light source installed in the exposure unit is in a power-on state where the power source is turned on, and the light source emits weak light in a standby light emission state. This includes cases where In this case, although the light source itself is in the standby light emission state, the potential unevenness in the main scanning direction given to the potential of the photosensitive drum is 7 V or less, and does not affect the inclination adjustment of the charger.

  In Example 1, a first adjustment toner image and a second adjustment toner image are formed. In Example 4, in addition to the first adjustment toner image and the second adjustment toner image, a third adjustment toner image is formed. Although an example in which the adjustment toner image is formed is shown, adjustment toner images other than the first to third adjustment toner images may be formed together.

1a to 1d photoconductor 2a to 2d corona charging device 3a to 3d exposure device 4a to 4d developing device 5a to 5d cleaning device 6a to 6d transfer roller 7 intermediate transfer member 8 secondary transfer device 9a to 9d neutralizing device 10 recording material storage device 11a to 11c In-machine temperature / humidity detection means 12 Out-of-machine temperature / humidity detection means 13 Fixing device 14a High voltage power supply 15 Operation panel 16 Execution button 21a Discharge wire 22a Grid electrode 23a Conductive shield 24a Adjustment screw 25a Adjustment piece 26a Grid inclination adjustment means 27 Support Piece 28 Screw member 29 Position adjustment member 30 Block 31 Front cover

Claims (6)

A photoreceptor,
A corona charger that is provided facing the surface of the photoconductor and charges the surface of the photoconductor;
Exposure means for exposing the surface of the photoreceptor charged by the corona charger and forming an electrostatic latent image on the surface of the photoreceptor;
Developing means for developing the electrostatic latent image formed by the exposure means with toner and forming a toner image on the surface of the photoreceptor;
Transfer means for transferring a toner image formed on the photoreceptor to a recording material;
First, an electrostatic latent image is formed by the exposure unit on the surface of the photosensitive member charged by the corona charger, and a toner image formed on the surface of the photosensitive member by the developing unit is transferred to a recording material for output. A plurality of modes formed on the surface of the photoconductor by the developing unit without substantially forming an electrostatic latent image on the surface of the photoconductor charged by the corona charger. Executing means for executing a second mode for transferring a plurality of toner images onto a recording material and outputting the toner images as a plurality of adjustment toner images for adjusting a distance from the surface of the photoreceptor in the longitudinal direction of the corona charger. Have
The execution means is in the second mode,
A toner image formed so that the average density is in the range of 0.4 to 0.8 when the charge amount per unit mass of the toner is 30 μC / g;
A toner image formed so that an average density is in a range of 0.4 to 0.8 when a charge amount per unit mass of toner is 45 μC / g is output as the plurality of toner images for adjustment. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein in the second mode, the execution unit transfers the plurality of adjustment toner images to one recording material and outputs the same.   The image forming apparatus according to claim 2, wherein in the second mode, the execution unit forms a blank portion where a toner image is not formed at both ends in the conveyance direction of the recording material. A developing bias applying means for applying a developing bias to the developing means;
The execution unit sets the development contrast, which is a potential difference between a DC voltage value of the developing bias and a potential of a toner image forming region on the surface of the photosensitive member, to a different value to form the plurality of toner images for adjustment. The image forming apparatus according to claim 1, wherein:   The execution means further includes a toner image formed so that an average density is in a range of 0.4 to 0.8 when a charge amount per unit mass of the toner is 10 μC / g. The image forming apparatus according to claim 1, wherein the image forming apparatus outputs the image as one of images. The image forming apparatus according to claim 1, wherein the developing device includes a developing container that stores a developer in which the toner and the magnetic carrier are mixed.

Images